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BACKGROUND Proper guidance of neuronal axons to their targets is required to assemble neural circuits during the development of the nervous system. However, the mechanism by which the guidance of axonal growth cones is regulated by specific intermediaries activated by receptor signaling pathways to mediate cytoskeleton dynamics is unclear. Vav protein members have been proposed to mediate this process, prompting us to investigate their role in the limb selection of the axon trajectory of spinal lateral motor column (LMC) neurons. RESULTS We found Vav2 and Vav3 expression in LMC neurons when motor axons grew into the limb. Vav2, but not Vav3, loss-of-function perturbed LMC pathfinding, while Vav2 gain-of-function exhibited the opposite effects, demonstrating that Vav2 plays an important role in motor axon growth. Vav2 knockdown also attenuated the redirectional phenotype of LMC axons induced by Dcc, but not EphA4, in vivo and lateral LMC neurite growth preference to Netrin-1 in vitro. This study showed that Vav2 knockdown and ectopic nonphosphorylable Vav2 mutant expression abolished the Src-induced stronger growth preference of lateral LMC neurites to Netrin-1, suggesting that Vav2 is downstream of Src in this context. CONCLUSIONS Vav2 is essential for Netrin-1-regulated LMC motor axon pathfinding through Src interaction.

Glioblastoma multiforme (GBM) is the most fatal cancer among brain tumors, and the standard treatment of GBM patients is surgical tumor resection followed by radiotherapy and temozolomide (TMZ) chemotherapy. However, tumors always recur due to the developing drug resistance. It has been shown that neurosteroids, including dehydroepiandrosterone and 17β-estradiol, are synthesized in TMZ-resistant GBM tumors. Therefore, we sought to explore the possible role of 17β-estradiol in the development of drug resistance in GBM. Bioinformatics analysis revealed that aromatase/cytochrome P450 19A1 expression was gradually increased in the development from normal, astrocytoma to GBM. The level of 17β-estradiol was significantly increased in TMZ-resistant cells characterized by ultra performance liquid chromatography-tandem mass spectrometry. Furthermore, 17β-estradiol attenuated TMZ-induced cell death and reduced reactive oxygen species production by mitochondria. In addition, 17β-estradiol attenuated oxidative stress by increasing the expression of superoxide dismutase 1/2, catalase, and nuclear factor erythroid 2-related factor (NRF) 2. We found that NRF2 expression was essential for the induction of drug resistance by 17β-estradiol through the reduction of oxidative stress in GBM.

To assemble the functional circuits of the nervous system, the neuronal axonal growth cones must be precisely guided to their proper targets, which can be achieved through cell–surface guidance receptor activation by ligand binding in the periphery. We investigated the function of paxillin, a focal adhesion protein, as an essential growth cone guidance intermediary in the context of spinal lateral motor column (LMC) motor axon trajectory selection in the limb mesenchyme. Usingin situmRNA detection, we first show paxillin expression in LMC neurons of chick and mouse embryos at the time of spinal motor axon extension into the limb. Paxillin loss-of-function and gain-of-function usingin ovoelectroporation in chick LMC neurons, of either sex, perturbed LMC axon trajectory selection, demonstrating an essential role of paxillin in motor axon guidance. In addition, a neuron-specific paxillin deletion in mice led to LMC axon trajectory selection errors. We also show that knocking down paxillin attenuates the growth preference of LMC neurites against ephrinsin vitro, and erythropoietin-producing human hepatocellular (Eph)-mediated retargeting of LMC axonsin vivo, suggesting paxillin involvement in Eph-mediated LMC motor axon guidance. Finally, both paxillin knockdown and ectopic expression of a nonphosphorylable paxillin mutant attenuated the retargeting of LMC axons caused by Src overexpression, implicating paxillin as a Src target in Eph signal relay in this context. In summary, our findings demonstrate that paxillin is required for motor axon guidance and suggest its essential role in the ephrin–Eph signaling pathway resulting in motor axon trajectory selection.SIGNIFICANCE STATEMENTDuring the development of neural circuits, precise connections need to be established among neurons or between neurons and their muscle targets. A protein family found in neurons, Eph, is essential at different stages of neural circuit formation, including nerve outgrowth and pathfinding, and is proposed to mediate the onset and progression of several neurodegenerative diseases, such as Alzheimer's disease. To investigate how Ephs relay their signals to mediate nerve growth, we investigated the function of a molecule called paxillin and found it important for the development of spinal nerve growth toward their muscle targets, suggesting its role as an effector of Eph signals. Our work could thus provide new information on how neuromuscular connectivity is properly established during embryonic development.

Temozolomide (TMZ) monotherapy is known to be insufficient for resistant/relapsed glioblastoma (GBM), thus seeking a sensitization agent for TMZ is necessary. It was found that regorafenib may improve the overall survival of relapsed GBM patients. We aimed to discover whether regorafenib can enhance the anti-GBM effects of TMZ, and elucidate underlying mechanism. Our analysis of The Cancer Genome Atlas database revealed that the increased expression of CXCR4 is linked to poor survival of GBM patients. Additionally, TMZ treatment may trigger CXCR4/CXCL12 axis of GBM. We used two GBM cell lines, two primary GBM cells, and animal model to identify underlying mechanism and treatment efficacy of regorafenib combined with TMZ by cytotoxicity, apoptosis, reporter gene and invasion/migration assays, chemokine array, Western blotting, MRI, microarray, and immunohistochemistry. We observed that the chemokine CXCL-12 and its receptor CXCR4 regulate the resistance to TMZ, whereas the inhibition of CXCL-12/CXCR4 signaling sensitizes GBM cells to TMZ. The TMZ-induced CXCL-12/CXCR4 signaling, phosphor-extracellular signal-regulated kinases 1 and 2 (ERK1/2) and nuclear factor kappa light chain enhancer of activated B cells (NF-κB), and NF-κB-related proteins can effectively diminish when combining with regorafenib. Regorafenib significantly enhanced the TMZ-induced extrinsic/intrinsic apoptotic pathways, and facilitated the suppression of invasion and migration potential in GBM. Orthotopic tumor experiments demonstrated tumor size reduction and prolonged survival in combination group even with half-dose of TMZ. Our findings provide promising evidence that regorafenib may sensitize GBM to TMZ treatment through inhibition of the CXCL12/CXCR4/ERK/NF-κB signaling. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13311-022-01194-y.

In seminiferous epithelium, tight junctions (TJs) between adjacent Sertoli cells constitute the blood-testis barrier and must change synchronically for germ cells to translocate from the basal to the adluminal compartment during the spermatogenic cycle. Rho GTPase activation through stimulation with specific L-selectin ligands has been proposed to modulate tight junctional dynamics. However, little is known regarding the role of Ca+2 dynamics in Sertoli cell and how Ca+2 relays L-selectin signals to modulate Rho GTPase activity in Sertoli cells, thus prompting us to investigate the Ca+2 flux induced by L-selectin ligand in ASC-17D cells. Using fluorescent real-time image, we first demonstrated the increase of intracellular Ca+2 level following L-selectin ligand stimulation. This Ca+2 increase was inhibited in ASC-17D cells pretreated with nifedipine, the L-type voltage-operated Ca+2 channel (VOCC) blocker, but not mibefradil, the T-type VOCC blocker. We then demonstrated the up-regulation of Rho and Rac1 in ASC-17D cells following the administration of L-selectin ligand, and the pre-treatment with nifedipine, but not mibefradil, prior to L-selectin ligand-binding abolished the activation of both Rho and Rac1. Together, we conclude that the activation of L-selectin induces Ca+2 influx through the L-type VOCC, which up-regulates Rho and Rac1 proteins, in ASC-17D cells.

Background Glioblastoma is associated with poor prognosis and high mortality. Although the use of first-line temozolomide can reduce tumor growth, therapy-induced stress drives stem cells out of quiescence, leading to chemoresistance and glioblastoma recurrence. The specificity protein 1 (Sp1) transcription factor is known to protect glioblastoma cells against temozolomide; however, how tumor cells hijack this factor to gain resistance to therapy is not known. Methods Sp1 acetylation in temozolomide-resistant cells and stemlike tumorspheres was analyzed by immunoprecipitation and immunoblotting experiments. Effects of the histone deacetylase (HDAC)/Sp1 axis on malignant growth were examined using cell proliferation–related assays and in vivo experiments. Furthermore, integrative analysis of gene expression with chromatin immunoprecipitation sequencing and the recurrent glioblastoma omics data were also used to further determine the target genes of the HDAC/Sp1 axis. Results We identified Sp1 as a novel substrate of HDAC6, and observed that the HDAC1/2/6/Sp1 pathway promotes self-renewal of malignancy by upregulating B cell-specific Mo-MLV integration site 1 (BMI1) and human telomerase reverse transcriptase (hTERT), as well as by regulating G2/M progression and DNA repair via alteration of the transcription of various genes. Importantly, HDAC1/2/6/Sp1 activation is associated with poor clinical outcome in both glioblastoma and low-grade gliomas. However, treatment with azaindolyl sulfonamide, a potent HDAC6 inhibitor with partial efficacy against HDAC1/2, induced G2/M arrest and senescence in both temozolomide-resistant cells and stemlike tumorspheres. Conclusion Our study uncovers a previously unknown regulatory mechanism in which the HDAC6/Sp1 axis induces cell division and maintains the stem cell population to fuel tumor growth and therapeutic resistance.

Background Sp1 is involved in the recurrence of glioblastoma (GBM) due to the acquirement of resistance to temozolomide (TMZ). Particularly, the role of Sp1 in metabolic reprogramming for drug resistance remains unknown. Methods RNA-Seq and mass spectrometry were used to analyze gene expression and metabolites amounts in paired GBM specimens (primary vs. recurrent) and in paired GBM cells (sensitive vs. resistant). ω-3/6 fatty acid and arachidonic acid (AA) metabolism in GBM patients were analyzed by targeted metabolome. Mitochondrial functions were determined by Seahorse XF Mito Stress Test, RNA-Seq, metabolome and substrate utilization for producing ATP. Therapeutic options targeting prostaglandin (PG) E2 in TMZ-resistant GBM were validated in vitro and in vivo. Results Among the metabolic pathways, Sp1 increased the prostaglandin-endoperoxide synthase 2 expression and PGE2 production in TMZ-resistant GBM. Mitochondrial genes and metabolites were obviously increased by PGE2, and these characteristics were required for developing resistance in GBM cells. For inducing TMZ resistance, PGE2 activated mitochondrial functions, including fatty acid β-oxidation (FAO) and tricarboxylic acid (TCA) cycle progression, through PGE2 receptors, E-type prostanoid (EP)1 and EP3. Additionally, EP1 antagonist ONO-8713 inhibited the survival of TMZ-resistant GBM synergistically with TMZ. Conclusion Sp1-regulated PGE2 production activates FAO and TCA cycle in mitochondria, through EP1 and EP3 receptors, resulting in TMZ resistance in GBM. These results will provide us a new strategy to attenuate drug resistance or to re-sensitize recurred GBM.

Background Sp1 is involved in the recurrence of glioblastoma (GBM) due to the acquirement of resistance to temozolomide (TMZ). Particularly, the role of Sp1 in metabolic reprogramming for drug resistance remains unknown. Methods RNA-Seq and mass spectrometry were used to analyze gene expression and metabolites amounts in paired GBM specimens (primary vs. recurrent) and in paired GBM cells (sensitive vs. resistant). ω-3/6 fatty acid and arachidonic acid (AA) metabolism in GBM patients were analyzed by targeted metabolome. Mitochondrial functions were determined by Seahorse XF Mito Stress Test, RNA-Seq, metabolome and substrate utilization for producing ATP. Therapeutic options targeting prostaglandin (PG) E2 in TMZ-resistant GBM were validated in vitro and in vivo. Results Among the metabolic pathways, Sp1 increased the prostaglandin-endoperoxide synthase 2 expression and PGE2 production in TMZ-resistant GBM. Mitochondrial genes and metabolites were obviously increased by PGE2, and these characteristics were required for developing resistance in GBM cells. For inducing TMZ resistance, PGE2 activated mitochondrial functions, including fatty acid β-oxidation (FAO) and tricarboxylic acid (TCA) cycle progression, through PGE2 receptors, E-type prostanoid (EP)1 and EP3. Additionally, EP1 antagonist ONO-8713 inhibited the survival of TMZ-resistant GBM synergistically with TMZ. Conclusion Sp1-regulated PGE2 production activates FAO and TCA cycle in mitochondria, through EP1 and EP3 receptors, resulting in TMZ resistance in GBM. These results will provide us a new strategy to attenuate drug resistance or to re-sensitize recurred GBM.

It has long been documented that cancer cells show increased and persistent oxidative stress due to increased reactive oxygen species (ROS), which is necessary for their increased proliferative rate. Due to the high levels of ROS, cancer cells also stimulate the antioxidant system, which includes the enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX), to eliminate ROS. However, overexpressed antioxidant enzymes often lead to drug resistance and therapeutic failure. Glioblastoma (GBM) is the most aggressive brain tumor and has the poorest prognosis. The transcription factor CCAAT/enhancer-binding protein delta (CEBPD) is highly expressed in GBM and correlates with drug resistance, prompting us to elucidate its role in GBM cell survival. In this study, we first demonstrated that loss of CEBPD significantly inhibited GBM cell viability and increased cell apoptosis. Furthermore, the expression of CAT was attenuated through promoter regulation following CEBPD knockdown, accelerating intracellular hydrogen peroxide (H

During the neural circuit formation, neuronal growth cones must be guided precisely to their neuronal or muscle targets, which can be achieved by the activation of membrane-bound guidance receptors at the periphery. However, the mechanisms that regulate the temporal availability of these receptors remain largely unknown. TAR DNA binding protein-43 (TDP-43) has been proposed to bind with the mRNAs of guidance receptors, thus prompting us to investigate its role in axon guidance of the spinal lateral motor column (LMC) neurons into the limb mesenchyme. We first identified the TDP-43 expression in the LMC neurons at the stage of axons growth into the limb using in situ mRNA hybridization. The loss and gain of TDP-43 function in chick LMC neurons redirected their axon trajectory with opposite effects. In mice, a spinal motor neuron-specific TDP-43 deletion led to the misrouting of LMC axons. Further, ectopic TDP-43 expression increased EphB protein levels in LMC neurons, suggesting that TDP-43 mediates LMC pathfinding by regulating EphB expression. Finally, TDP-43 levels influenced the growth preference of LMC neurites against ephrin-B, but not Netrin-1 and Semaphorin ligands. Our results demonstrate that TDP-43 is essential for the ephrinB:EphB signaling-mediated axon trajectory selection of LMC subtypes into the limb.

Allopregnanolone (allo) is a physiological regulator of neuronal activity that treats multiple neurological disorders. Allo penetrates the blood-brain barrier with very high efficiency, implying that allo can treat CNS-related diseases, including glioblastoma (GBM), which always recurs after standard therapy. Hence, this study aimed to determine whether allo has a therapeutic effect on GBM. We found that allo enhanced temozolomide (TMZ)-suppressed cell survival and proliferation of TMZ-resistant cells. In particular, allo enhanced TMZ-inhibited cell migration and TMZ-induced apoptosis. Additionally, allo strongly induced DNA damage characterized by γH2Ax. Furthermore, quantitative proteomic analysis, iTRAQ, showed that allo significantly decreased the levels of DPYSL3, S100A11, and S100A4, reflecting the poor prognosis of patients with GBM confirmed by differential gene expression and survival analysis. Moreover, single-cell RNA-Seq revealed that S100A11, expressed in malignant cells, oligodendrocytes, and macrophages, was significantly associated with immune cell infiltration. Furthermore, overexpression of DPYSL3 or S100A11 prevented allo-induced cell death. In conclusion, allo suppresses GBM cell survival by decreasing DPYSL3/S100A11 expression and inducing DNA damage.

DNA repair promotes the progression and recurrence of glioblastoma (GBM). However, there remain no effective therapies for targeting the DNA damage response and repair (DDR) pathway in the clinical setting. Thus, we aimed to conduct a comprehensive analysis of DDR genes in GBM specimens to understand the molecular mechanisms underlying treatment resistance. Herein, transcriptomic analysis of 177 well-defined DDR genes was performed with normal and GBM specimens (n = 137) from The Cancer Genome Atlas and further integrated with the expression profiling of histone deacetylase 6 (HDAC6) inhibition in temozolomide (TMZ)-resistant GBM cells and patient-derived tumor cells. The effects of HDAC6 inhibition on DDR signaling were examined both in vitro and intracranial mouse models. We found that the expression of DDR genes, involved in repair pathways for DNA double-strand breaks, was upregulated in highly malignant primary and recurrent brain tumors, and their expression was related to abnormal clinical features. However, a potent HDAC6 inhibitor, MPT0B291, attenuated the expression of these genes, including RAD51 and CHEK1, and was more effective in blocking homologous recombination repair in GBM cells. Interestingly, it resulted in lower cytotoxicity in primary glial cells than other HDAC6 inhibitors. MPT0B291 reduced the growth of both TMZ-sensitive and TMZ-resistant tumor cells and prolonged survival in mouse models of GBM. We verified that HDAC6 regulated DDR genes by affecting Sp1 expression, which abolished MPT0B291-induced DNA damage. Our findings uncover a regulatory network among HDAC6, Sp1, and DDR genes for drug resistance and survival of GBM cells. Furthermore, MPT0B291 may serve as a potential lead compound for GBM therapy.

In this study, we found that Sp1 was highly expressed in astrocytes, implying that Sp1 might be important for the function of astrocytes. Sp1/GFAP-Cre-ERT2 conditional knockout mice were constructed to study the role of Sp1 in astrocytes. Knockout of Sp1 in astrocytes altered astrocytic morphology and decreased GFAP expression in the cortex and hippocampus but did not affect cell viability. Loss of Sp1 in astrocytes decreased the number of neurons in the cortex and hippocampus. Conditioned medium from primary astrocytes with Sp1 knockout disrupted neuronal dendritic outgrowth and synapse formation, resulting in abnormal learning, memory, and motor behavior. Sp1 knockout in astrocytes altered gene expression, including decreasing the expression of Toll-like receptor 2 and Cfb and increasing the expression of C1q and C4Bp, thereby affecting neurite outgrowth and synapse formation, resulting in disordered neuron function. Studying these gene regulations might be beneficial to understanding neuronal development and brain injury prevention.

Although histone deacetylase 8 (HDAC8) plays a role in glioblastoma multiforme (GBM), whether its inhibition facilitates the treatment of temozolomide (TMZ)-resistant GBM (GBM-R) remains unclear. By assessing the gene expression profiles from short hairpin RNA of HDAC8 in the new version of Connectivity Map (CLUE) and cells treated by NBM-BMX (BMX)-, an HDAC8 inhibitor, data analysis reveals that the Wnt signaling pathway and apoptosis might be the underlying mechanisms in BMX-elicited treatment. This study evaluated the efficacy of cotreatment with BMX and TMZ in GBM-R cells. We observed that cotreatment with BMX and TMZ could overcome resistance in GBM-R cells and inhibit cell viability, markedly inhibit cell proliferation, and then induce cell cycle arrest and apoptosis. In addition, the expression level of β-catenin was reversed by proteasome inhibitor via the β-catenin/ GSK3β signaling pathway to reduce the expression level of c-Myc and cyclin D1 in GBM-R cells. BMX and TMZ cotreatment also upregulated WT-p53 mediated MGMT inhibition, thereby triggering the activation of caspase-3 and eventually leading to apoptosis in GBM-R cells. Moreover, BMX and TMZ attenuated the expression of CD133, CD44, and SOX2 in GBM-R cells. In conclusion, BMX overcomes TMZ resistance by enhancing TMZ-mediated cytotoxic effect by downregulating the β-catenin/c-Myc/SOX2 signaling pathway and upregulating WT-p53 mediated MGMT inhibition. These findings indicate a promising drug combination for precision personal treating of TMZ-resistant WT-p53 GBM cells.

B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) appears to be essential for promoting certain types of cancer, and its inhibition effectively reduced the stemness of cancer cells. Therefore, this study aimed to investigate the potential role of BMI1 in glioma. To this end, we first investigated BMI1 expression in brain tumors using microarray datasets in ONCOMINE, which indicated that BMI1 levels were not commonly increased in clinical brain tumors. Moreover, survival plots in PROGgeneV2 also showed that BMI1 expression was not significantly associated with reduced survival in glioma patients. Interestingly, stressful serum deprivation and anchorage independence growth conditions led to an increased BMI1 expression in glioma cells. A stress-responsive pathway, HDAC/Sp1, was further identified to regulate BMI1 expression. The HDAC inhibitor vorinostat (SAHA) prevented Sp1 binding to the BMI1 promoter, leading to a decreased expression of BMI1 and attenuating tumor growth of TMZ-resistant glioma xenografts. Importantly, we further performed survival analysis using PROGgeneV2 and found that an elevated expression of HDAC1,3/Sp1/BMI1 but not BMI1 alone showed an increased risk of death in both high- and low-grade glioma patients. Thus, HDAC-mediated Sp1 deacetylation is critical for BMI1 regulation to attenuate stress- and therapy-induced death in glioma cells, and the HDAC/Sp1 axis is more important than BMI1 and appears as a therapeutic target to prevent recurrence of malignant glioma cells persisting after primary therapy.

Hurdled and marred by the notorious nature of glioblastomas (GBM) in terms of resistance to therapy and limited drug delivery into the brain, the anti-GBM drug pipeline is required to be loaded with mechanistically diverse agents. The consideration of HDAC inhibition as a prudent approach to circumvent the resistance issue in GBM spurred us to pragmatically design and synthesizes hydroxamic acids endowed with CNS penetrating ability. By virtue of the blood brain barrier permeability (BBB), memantine was envisioned as an appropriate CAP component for the construction of the HDAC inhibitors. Diverse linkers were stapled for the tetheration of the zinc binding motif with the CAP group to pinpoint an appropriate combination (CAP and linker) that could confer inhibitory preference to HDAC6 isoform (overexpressed in GBM). Resultantly, hydroxamic acid 16 was identified as a promising compound that elicited striking antiproliferative effects against Human U87MG GBM cells as well as TMZ-resistant GBM cells and P1S cells, a concurrent chemo radiotherapy (CCRT)-resistant/patient-derived glioma cell line mediated through preferential HDAC6 inhibition (IC50 = 5.42 nM). Furthermore, 16 exerted cell cycle arrest at G2 phase, induced apoptosis in GBM cells at high concentration and exhibited high BBB permeability. To add on, in-vivo study revealed that the administration of compound 16 prolonged the survival of TMZ-resistant U87MG inoculated orthotopic mice. Overall, the cumulative results indicate that 16 is a tractable CNS penetrant preferential HDAC6 inhibitor that might emerge as a potent weapon against GBM.

Patients with glioblastoma are at high risk of local recurrences after initial treatment with standard therapy, and recurrent tumor cells appear to be resistant to first-line drug temozolomide. Thus, finding an effective second-line agent for treating primary and recurrent glioblastomas is critical. Betulinic acid (BA), a natural product of plant origin, can cross the blood&ndash, brain barrier. Here, we investigated the antitumor effects of BA on typical glioblastoma cell lines and primary glioblastoma cells from patients, as well as corresponding temozolomide-resistant cells. Our findings verified that BA significantly reduced growth in all examined cells. Furthermore, gene-expression array analysis showed that the unfolded-protein response was significantly affected by BA. Moreover, BA treatment increased activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK)/C/EBP homologous protein (CHOP) apoptotic pathway, and reduced specificity protein 1 (Sp1) expression. However, Sp1 overexpression reversed the observed cell-growth inhibition and PERK/CHOP signaling activation induced by BA. Because temozolomide-resistant cells exhibited significantly increased Sp1 expression, we concluded that Sp1-mediated PERK/CHOP signaling inhibition protects glioblastoma against cancer therapies, hence, BA treatment targeting this pathway can be considered as an effective therapeutic strategy to overcome such chemoresistance and tumor relapse.

In seminiferous epithelium, tight junctions (TJs) between adjacent Sertoli cells constitute the blood-testis barrier and must change synchronically for germ cells to translocate from the basal to the adluminal compartment during the spermatogenic cycle. Rho GTPase activation through stimulation with specific L-selectin ligands has been proposed to modulate tight junctional dynamics. However, little is known regarding the role of Ca

The accumulation of reactive oxygen species (ROS) commonly occurs during normal aging and during some acute/chronic progressive disorders. In order to avoid oxidative damage, scavenging of these radicals is important. Previously, we identified zinc finger protein 179 (Znf179) as a neuroprotector that increases antioxidant enzymes against superoxide radicals. However, the molecular mechanisms involved in the activation and regulation of Znf179 remain unresolved. Here, by performing sequence alignment, bioinformatics analysis, immunoprecipitation using two specific acetyl-lysine antibodies, and treatment with the histone deacetylase (HDAC) inhibitor SAHA, we determined the lysine-specific acetylation of Znf179. Furthermore, we investigated Znf179 interaction with HDACs and revealed that peroxide insult induced a dissociation of Znf179-HDAC1/HDAC6, causing an increase in Znf179 acetylation. Importantly, HDAC inhibition by SAHA further prompted Znf179 hyperacetylation, which promoted Znf179 to form a transcriptional complex with Sp1 and increased antioxidant gene expression against oxidative attack. In summary, the results obtained in this study showed that Znf179 was regulated by HDACs and that Znf179 acetylation was a critical mechanism in the induction of antioxidant defense systems. Additionally, HDAC inhibitors may have therapeutic potential for induction of Znf179 acetylation, strengthening the Znf179 protective functions against neurodegenerative processes., Highlights • Zinc finger protein 179 (Znf179) is regulated by histone deacetylase (HDAC). • Acetylation of Znf179 is lysine specific. • Znf179 acetylation induces antioxidant defense systems. • HDAC inhibitors may have therapeutic potential as inducers of Znf179 acetylation.

Background The development of a functioning nervous system requires precise assembly of neuronal connections, which can be achieved by the guidance of axonal growth cones to their proper targets. How axons are guided by signals transmitted to the cytoskeleton through cell surface-expressed guidance receptors remains unclear. We investigated the function of Nck2 adaptor protein as an essential guidance intermediary in the context of spinal lateral motor column (LMC) motor axon trajectory into the limb. Results Nck2 mRNA and protein are preferentially expressed in the medial subgroups of chick LMC neurons during axon trajectory into the limb. Nck2 loss- and gain-of-function in LMC neurons using in ovo electroporation perturb LMC axon trajectory selection demonstrating an essential role of Nck2 in motor axon guidance. We also showed that Nck2 knockdown and overexpression perturb the growth preference of LMC neurites against ephrins in vitro and Eph-mediated redirection of LMC axons in vivo. Finally, the significant changes of LMC neurite growth preference against ephrins in the context of Nck2 and α2-chimaerin loss- and gain-of-function implicated Nck2 function to modulate α2-chimaerin activity. Conclusions Here, we showed that Nck2 is required for Eph-mediated axon trajectory selection from spinal motor neurons through possible interaction with α2-chimaerin. Developmental Dynamics 247:1043-1056, 2018. © 2018 Wiley Periodicals, Inc.

Drug resistance is the main obstacle in the improvement of chemotherapeutic efficacy in glioblastoma. Previously, we showed that dehydroepiandrosterone (DHEA), one kind of androgen/neurosteroid, potentiates glioblastoma to acquire resistance through attenuating DNA damage. Androgen receptor (AR) activated by DHEA or other types of androgen was reported to promote drug resistance in prostate cancer. However, in DHEA-enriched microenvironment, the role of AR in acquiring resistance of glioblastoma remains unknown. In this study, we found that AR expression is significantly correlated with poor prognosis, and AR obviously induced the resistance to temozolomide (TMZ) treatment. Herein, we observed that ALZ003, a curcumin analog, induces FBXL2-mediated AR ubiquitination, leading to degradation. Importantly, ALZ003 significantly inhibited the survival of TMZ-sensitive and –resistant glioblastoma in vitro and in vivo. The accumulation of reactive oxygen species (ROS), lipid peroxidation and suppression of glutathione peroxidase (GPX) 4, which are characteristics of ferroptosis, were observed in glioblastoma cell after treatment of ALZ003. Furthermore, overexpression of AR prevented ferroptosis in the presence of GPX4. To evaluate the therapeutic effect in vivo, we transplanted TMZ-sensitive or -resistant U87MG cells into mouse brain followed by intravenous administration with ALZ003. In addition to inhibiting the growth of glioblastoma, ALZ003 significantly extended the survival period of transplanted mice, and significantly decreased AR expression in the tumor area. Taken together, AR potentiates TMZ resistance for glioblastoma, and ALZ003-mediated AR ubiquitination might open a new insight into therapeutic strategy for TMZ resistant glioblastoma., Graphical abstract Image 1, Highlights • ALZ003, the curcumin analog, inhibits TMZ–resistant glioblastoma. • ALZ003 induces AR degradation through FBXL2-mediated ubiquitination. • ALZ003 induces ferroptosis through blocking AR-mediated GPX4 expression. • ALZ003 increases ROS and lipid peroxidation through reducing GPX4 expression.

Glioblastoma is the most malignant type of brain tumor for which there are currently no effective treatments. Patient prognosis is improved by radiation combined with temozolomide (TMZ) therapy but only for a short period of time due to the high prevalence of recurrence. Although O6-methylguanine-DNA methyltransferase (MGMT)-mediated DNA repair is a well-defined characteristic of TMZ resistance, the mechanism by which MGMT-deficient glioblastoma counteracts TMZ-induced DNA damage, leading to apoptosis, still remains unclear. Previously, we determined that aberrantly activated cytochrome P450 17A1 causes TMZ resistance in MGMT-deficient glioblastoma by increasing the secretion of dehydroepiandrosterone (DHEA), a neurosteroid that maintains the health of neurons and astrocytes. However, the precise mechanism by which DHEA alters the response of glioblastoma to TMZ has not been studied. In the present study, we found that DHEA prevents TMZ-induced apoptosis by attenuating DNA damage in MGMT-deficient glioblastoma. In addition, DHEA activated the LYN-AKT cascade to induce Sp1 phosphorylation. Phospho-Sp1 localized in TMZ-damaged DNA, prevented further DNA damage, and was deacetylated through the recruitment of HDAC1/2. Deacetylated Sp1 recruited proliferating cell nuclear antigen (PCNA) to attenuate DNA damage. To confirm whether the DHEA-induced cellular process contributes to TMZ resistance, we established a TMZ-resistant glioblastoma cell line, A172R, and isolated primary resistant tumor cells, PtR#1, from a glioblastoma patient exhibiting chemotherapeutic resistance. Sp1 exhibited phosphorylated and deacetylated status, and associated with HDAC1/2 and PCNA in TMZ-resistant cells. Based on these findings, we conclude that DHEA induces TMZ resistance in glioblastoma via the induction of phospho-Sp1-mediated DNA repair.

It has been suggested that stress stimuli from the microenvironment maintain a subset of tumor cells with stem-like properties, including drug resistance. Here, we investigate whether Sp1, a stress-responsive factor, regulates stemness gene expression and if its inhibition sensitizes cancer cells to chemotherapy. Hydrogen peroxide- and serum deprivation-induced stresses were performed in glioblastoma (GBM) cells and patient-derived cells, and the effect of the Sp1 inhibitor mithramycin A (MA) on these stress-induced stem cells and temozolomide (TMZ)-resistant cells was evaluated. Sp1 and stemness genes were not commonly overexpressed in clinical GBM samples. However, their expression was highly induced by stress stimuli. Using MA, we demonstrated Sp1 as a critical stemness-related transcriptional factor protecting GBM cells against stress- and TMZ-induced death. Thus, Sp1 inhibition may prevent recurrence of malignant cells persisting after primary therapy.

Acquisition of temozolomide (TMZ) resistance is a major factor leading to the failure of glioblastoma (GBM) treatment. The exact mechanism by which GBM evades TMZ toxicity is not always related to the expression of the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), and so remains unclear. In this study, TMZ-resistant variants derived from MGMT-negative GBM clinical samples and cell lines were studied, revealing there to be increased specificity protein 1 (Sp1) expression associated with reduced reactive oxygen species (ROS) accumulation following TMZ treatment. Analysis of gene expression databases along with cell studies identified the ROS scavenger superoxide dismutase 2 (SOD2) as being disease-related. SOD2 expression was also increased, and it was found to be co-expressed with Sp1 in TMZ-resistant cells. Investigation of the SOD2 promoter revealed Sp1 as a critical transcriptional activator that enhances SOD2 gene expression. Co-treatment with an Sp1 inhibitor restored the inhibitory effects of TMZ, and decreased SOD2 levels in TMZ-resistant cells. This treatment strategy restored susceptibility to TMZ in xenograft animals, leading to prolonged survival in an orthotopic model. Thus, our results suggest that Sp1 modulates ROS scavengers as a novel mechanism to increase cancer malignancy and resistance to chemotherapy. Inhibition of this pathway may represent a potential therapeutic target for restoring treatment susceptibility in GBM.

Glioblastoma multiforme (GBM) is the most fatal of all brain cancers, and the standard care protocol for GBM patients is surgical tumor resection followed by radiotherapy and temozolomide (TMZ)-mediated chemotherapy. However, tumor recurrence frequently occurs, and recurrent GBM exhibits more malignancy and less sensitivity in response to chemotherapy. The malignancy and drug resistance primarily reflect the small population of glioma stem-like cells (GSC). Therefore, understanding the mechanism that controls GSC enrichment is important to benefit the prognosis of GBM patients. Nucleolin (NCL), which is responsible for ribosome biogenesis and RNA maturation, is overexpressed in gliomas. However, the role of NCL in GSC development and drug resistance is still unclear. In this study, we demonstrate that NCL attenuated GSC enrichment to enhance the sensitivity of GBM cells in response to TMZ. In GSC enrichment, NCL was significantly reduced at the protein level as a result of decreased protein stability. In particular, the inhibition of HDAC activity by suberoylanilide hydroxamic acid rescued NCL acetylation accompanied by the loss of mouse double minute 2 homolog (MDM2)-mediated ubiquitination. In addition, we found that NCL ubiquitination resulted from the activation of STAT3- and JNK-mediated signaling in GSC. Moreover, NCL inhibited the formation of stem-like spheres by attenuating the expression of Sox2, Oct4, and Bmi1. Furthermore, NCL sensitized the response of GBM cells to TMZ. Based on these findings, NCL expression is a potential indicator to predict chemotherapeutic efficiency in GBM patients.

Glioblastoma (GBM) is the most aggressive type of brain tumor, with strong invasiveness and a high tolerance to chemotherapy. Despite the current standard treatment combining temozolomide (TMZ) and radiotherapy, glioblastoma can be incurable due to drug resistance. The existence of glioma stem-like cells (GSCs) is considered the major reason for drug resistance. However, the mechanism of GSC enrichment remains unclear. Herein, we found that the expression and secretion of angiopoietin-like 4 protein (ANGPTL4) were clearly increased in GSCs. The overexpression of ANGPTL4 induced GSC enrichment that was characterized by polycomb complex protein BMI-1 and SRY (sex determining region Y)-box 2 (SOX2) expression, resulting in TMZ resistance in GBM. Furthermore, epidermal growth factor receptor (EGFR) phosphorylation induced 4E-BP1 phosphorylation that was required for ANGPTL4-induced GSC enrichment. In particular, ANGPTL4 induced 4E-BP1 phosphorylation by activating phosphoinositide 3-kinase (PI3K)/AKT and extracellular signal&ndash, regulated kinase (ERK) cascades for inducing stemness. To elucidate the mechanism contributing to ANGPTL4 upregulation in GSCs, chromatin immunoprecipitation coupled with sequencing (ChIP-Seq) revealed that specificity protein 4 (Sp4) was associated with the promoter region, &minus, 979 to &minus, 606, and the luciferase reporter assay revealed that Sp4 positively regulated activity of the ANGPTL4 promoter. Moreover, both ANGPTL4 and Sp4 were highly expressed in GBM and resulted in a poor prognosis. Taken together, Sp4-mediated ANGPTL4 upregulation induces GSC enrichment through the EGFR/AKT/4E-BP1 cascade.

Background Intratumor subsets with tumor-initiating features in glioblastoma are likely to survive treatment. Our goal is to identify the key factor in the process by which cells develop temozolomide (TMZ) resistance. Methods Resistant cell lines derived from U87MG and A172 were established through long-term co-incubation of TMZ. Primary tumors obtained from patients were maintained as patient-derived xenograft for studies of tumor-initating cell (TIC) features. The cell manifestations were assessed in the gene modulated cells for relevance to drug resistance. Results Among the mitochondria-related genes in the gene expression databases, superoxide dismutase 2 (SOD2) was a significant factor in resistance and patient survival. SOD2 in the resistant cells functionally determined the cell fate by limiting TMZ-stimulated superoxide reaction and cleavage of caspase-3. Genetic inhibition of the protein led to retrieval of drug effect in mouse study. SOD2 was also associated with the TIC features, which enriched in the resistant cells. The CD133+ specific subsets in the resistant cells exhibited superior superoxide regulation and the SOD2-related caspase-3 reaction. Experiments applying SOD2 modulation showed a positive correlation between the TIC features and the protein expression. Finally, co-treatment with TMZ and the SOD inhibitor sodium diethyldithiocarbamate trihydrate in xenograft mouse models with the TMZ-resistant primary tumor resulted in lower tumor proliferation, longer survival, and less CD133, Bmi-1, and SOD2 expression. Conclusion SOD2 plays crucial roles in the tumor-initiating features that are related to TMZ resistance. Inhibition of the protein is a potential therapeutic strategy that can be used to enhance the effects of chemotherapy. Graphical abstract

Cytochrome P450 (CYP) 17A1 is an important steroidogenic enzyme harboring 17&alpha, hydroxylase and performing 17,20 lyase activities in multiple steps of steroid hormone synthesis, including dehydroepiandrosterone (DHEA) biosynthesis. Previously, we showed that CYP17A1-mediated DHEA production clearly protects glioblastomas from temozolomide-induced apoptosis, leading to drug resistance. Herein, we attempt to clarify whether the inhibition of CYP17A1 has a tumor-suppressive effect, and to determine the steroidogenesis-independent functions of CYP17A1 in glioblastomas. Abiraterone, an inhibitor of CYP17A1, significantly inhibits the proliferation of A172, T98G, and PT#3 (the primary glioblastoma cells) by inducing apoptosis. In parallel, abiraterone potently suppresses tumor growth in mouse models through transplantation of PT#3 cells to the back or to the brain. Based on evidence that abiraterone induces endoplasmic reticulum (ER) stress, followed by the accumulation of reactive oxygen species (ROS), CYP17A1 is important for ER health and redox homeostasis. To confirm our hypothesis, we showed that CYP17A1 overexpression prevents the initiation of ER stress and attenuates ROS production by regulating SAR1a/b expression. Abiraterone dissociates SAR1a/b from ER-localized CYP17A1, and induces SAR1a/b ubiquitination, leading to degradation. Furthermore, SAR1 overexpression rescues abiraterone-induced apoptosis and impairs redox homeostasis. In addition to steroid hormone synthesis, CYP17A1 associates with SAR1a/b to regulate protein processing and maintain ER health in glioblastomas.

Background The small population of glioma stem-like cells (GSCs) contributes to tumor initiation, malignancy, and recurrence in glioblastoma. However, the maintenance of GSC properties in the tumor microenvironment remains unclear. In glioma, non-neoplastic cells create an inflammatory environment and subsequently mediate tumor progression and maintenance. Transcriptional factor CCAAT/enhancer-binding protein delta (CEBPD) is suggested to regulate various genes responsive to inflammatory cytokines, thus prompting us to investigate its role in regulating GSCs stemness after inflammatory stimulation. Methods Stemness properties were analyzed by using spheroid formation. Oncomine and TCGA bioinformatic databases were used to analyze gene expression. Western blotting, quantitative real-time polymerase chain reaction, luciferase reporter assay, and chromatin immunoprecipitation assay were used to analyze proteins and gene transcript levels. The glioma tissue microarrays were used for CEBPD and PDGFA expression by immunohistochemistry staining. Results We first found that IL-1β promotes glioma spheroid formation and is associated with elevated CEBPD expression. Using microarray analysis, platelet-derived growth factor subunit A (PDGFA) was confirmed as a CEBPD-regulated gene that mediates IL-1β-enhanced GSCs self-renewal. Further analysis of the genomic database and tissue array revealed that the expression levels between CEBPD and PDGFA were coincident in glioma patient samples. Conclusion This is the first report showing the activation of PDGFA expression by CEBPD through IL-1β treatment and a novel CEBPD function in maintaining the self-renewal feature of GSCs. Electronic supplementary material The online version of this article (10.1186/s12974-019-1535-z) contains supplementary material, which is available to authorized users.

During brain development, the expression of promyelocytic leukemia zinc finger (Plzf) in neural stem cells is precisely controlled to maintain the balance between neural stem cell self-renewal and differentiation. However, the mechanism underlying transcriptional regulation of Plzf in neural stem cell is still unclear. Herein, using P19 embryonal carcinoma cells as a model, we observed that Plzf expression was induced in the P19-derived embryonic bodies, which enrich neural stem-like cell populations, as demonstrated by the expression of neural stem cell markers, Nestin and Sox2. We then characterized the Plzf promoter and identified two E2f1 binding sites (−755/-751 and −53/-49, the transcription start site was designated as +1) are important for the activation of Plzf promoter. Finally, we found that the induction of Plzf in the neural stem-like cells derived from pluripotent P19 cells is decrease by E2f1 knockdown. Taken together, we conclude that E2f1 is an important transcription factor that regulates Plzf transcription and may involve in maintaining the self-renewal ability of neural stem cells.

Additional file 3: Figure S3. The mitochondrial ROS were detected with MitoSox. (A) The TMZ-induced mitochondrial ROS were in parental and resistant U87MG cells. (B) The MitoSox results of CD133+ cells from U87MG parental and resistant cells were presented. The black curves represented the unstained control, the green curves represented the untreated group, and the pink curves represented the treated group. The brackets were the mean fluorescent intensity. These plots were representative ones of the triplicate experiments.